Isolating soil organic carbon (SOC) from soil inorganic carbon (SIC) is necessary to quantify SOC stocks and understanding SOC dynamics. Inorganic acids are commonly used to remove SIC and several methods have been developed to minimize the impacts these acid treatments have on the residual SOC. Negative impacts on the SOC pool, such as underestimating SOC stocks, are caused in part due to differences in the amount and composition of the organic matter pool. The effects of SIC removal on SOC are often ignored within experimental studies based on the assumption that soils from the same site do not differ enough to impact results. However, some experimental treatments, such as elevated atmospheric CO₂, change SOC pools in both concentration and composition. Therefore, SIC removal can introduce different biases in control and treatment soils that may differ by method. In this work, we compare two commonly used methods of SIC removal on a set of soil samples from the same elevated CO₂ experiment. We use soils from the Nevada Desert Free Air Carbon dioxide Enrichment Facility to quantify how SIC removal with either acid washing or acid fumigation affect SOC in control and elevated CO₂ plots. We then use the difference in SOC (%C and δ¹³C) between methods to infer changes in the SOC pool driven by the elevated CO₂ treatment. Our results show that acid washing underestimates SOC relative to fumigation and that this difference is larger in soils from control CO₂ plots than elevated CO₂ plots. This may suggest that stabilization mechanisms sensitive to acidification, such as calcium bridging, are disrupted under elevated CO₂ treatment and therefore are less susceptible to SOC loss during acid washing. Our results present future research avenues for exploring the effects of acidic organic compounds, such as root exudates, on SOC stability in alkaline soils.

将土壤有机碳 (SOC) 与土壤无机碳 (SIC) 分离对于量化 SOC 储量和了解 SOC 动态至关重要。无机酸通常用于去除 SIC，并且已经开发了多种方法来最大限度地减少这些酸处理对残留 SOC 的影响。对 SOC 库的负面影响，例如低估 SOC 库，部分是由于有机物库的数量和组成的差异造成的。基于同一地点的土壤差异不足以影响结果的假设，实验研究中经常忽略 SIC 去除对 SOC 的影响。然而，一些实验性处理，例如升高大气CO ₂，改变 SOC 池的浓度和成分。因此，SIC 去除可能会在控制和处理土壤中引入不同的偏差，这些偏差可能因方法而异。_{在这项工作中，我们比较了对来自同一高 CO 2} 实验的一组土壤样品去除 SIC 的两种常用方法。我们使用来自内华达沙漠自由空气二氧化碳富集设施的土壤来量化通过酸洗或酸熏蒸去除 SIC 如何影响对照和高 CO 2 地块中的_SOC。然后，我们使用不同方法之间 SOC（%C 和 δ ^{13 C）的差异来推断由 CO} ₂升高驱动的 SOC 池的变化治疗。我们的结果表明，相对于熏蒸，酸洗低估了 SOC，并且这种差异在对照 CO ₂地块的土壤中比高 CO ₂地块的土壤中更大。_{这可能表明对酸化敏感的稳定机制（例如钙桥）在升高的CO 2}处理下被破坏，因此在酸洗过程中不太容易受到SOC损失的影响。我们的研究结果为探索酸性有机化合物（例如根系分泌物）对碱性土壤中 SOC 稳定性的影响提供了未来的研究途径。